Effects Of Intrinsic And Extrinsic Noises On Transposons Kinetics

Fluctuation(or noise)phenomenon is ubiquitous in various biological systems,existing over multiple scales of biological systems from population level to molecular level.This has been widely studied in the context of coupled limit cycle oscillator models,for instance,the population systems(such as the predator-prey model),the excitable cells(such as the neuron model),and the intracellular signaling systems(such as the calcium oscillation model).The transposable elements(TEs)are the DNA sequences which can change its position within a genome.In a eukaryotic cell,the TEs play a critical role in genome function and evolution.The edit operation of TEs on the host genome is separated into two types:one is the "copy and paste",and the other is the "cut and paste".Some transposons(such as the autonomous long interspersed nuclear elements,LINEs)encode the enzymes which perform their excision,while others are parasitic(such as the non autonomous short interspersed nuclear elements,SINEs),relying on the enzymes produced by the regular TEs.Although fluctuations are ubiquitous in various biological systems,the absolute concentration robustness(ACR)steady state of a biochemical system can protect against changing a large concentration of the system's components.In this thesis,based on a minimal model of the interactions between LINEs and SINEs,the effects of the intrinsic and extrinsic noises on this system are investigated,respectively.The effects of intrinsic and extrinsic noises on ACR steady state of the transposons kinetics are studied by numerical simulations.It is found that the predator-prey like oscillations around the ACR steady state are induced by the intrinsic or extrinsic noises:(i)Under the same noise intensity,the amplitude of oscillations induced by intrinsic noises is larger than that by extrinsic noises.With the increasing of noise intensity,the peak distribution probability of the system is shifted from the second steady state to the first steady state,and both extrinsic and intrinsic noises can enlarge the width of the probability distribution.(ii)For both the additive and multiplicative noises cases,the larger the noise intensity is,the faster the attenuation of oscillations of auto-correlation and cross-correlation functions will be.The correlation time corresponding to the first peak of the cross-correlation function can represent the time delay of predator-prey like oscillations between nonautonomous transposons with autonomous ones.(iii)The state of the predator-prey oscillator induced by noises is stored in the genome and transmitted to 50 successive generations at least.